In this paper, we present empirical findings from a mixed-methods study of an Evaluation Capacity Building (ECB) initiative called the Partnerships for Advancing Character program Evaluation (PACE) Project that applied the Relational Systems Evaluation (RSE) approach. We focused especially on how participation in this partnership-based ECB program is associated with changes in attitudes and behaviors related to evaluation capacity and Evaluative Thinking. We used a repeated measures design with semi-structured interviews and surveys to examine two research questions: (1) Do Program Professionals participating in PACE adopt Evaluative Thinking behaviors? And (2) Do Program Professionals participating in PACE demonstrate increased evaluation capacity, including improved attitudes about evaluation? We found that PACE successfully increased Program Professional's behaviors, attitudes, and capacity; in particular, participants overwhelmingly noted that the emphasis on Evaluative Thinking changed the way they think about and approach evaluation, such that evaluation is now more well-integrated into their practice.